In a known way, the latter consist of two parallel plates produced by molding, at a distance from each other, from a hydraulic mixture, such as concrete, and of a built-in metal reinforcement, said plates being separated by an insulating block and connected together through transverse spacers.
Thus, these elements are brought onto the building site for immediate use, without any further preparation, if not having to connect them together in a preferentially simple, effective and economical way.